Looking into this further, there's a few things that could be the cause of the non playing sound issue for some in FireFox.
First up is of course any ad blocker. If Ad Block Plus is blocking the sounds from playing then it isn't being very smart about what's an Ad or other pup (potentially unwanted program, pup is a term but program doesn't really fit here but for the lack of a better word). I've not used Ad Block Plus (I block at the DNS level with a PiHole) so I can't say what sort of fine grain control you have over it.
Secondly, the source of the sounds page is a mess. If browsers weren't so good a guessing what should be there the page wouldn't render at all, what with all the missing and misplaced tags. The page also uses the incorrect media type to tell the browser what media type the sound files are.
As a test to see if the page source / incorrect media type is the issue you can go here to test playing a sound with the correct source and correct media type:
https://www.w3schools.com/TAGS/tryit.asp?filename=tryhtml5_audio. As the RailPro sounds page uses mp3's delete the horse.ogg line and click the run button to test just the mp3 file.
And lastly, there's not that many sound files there to play. The page displays the controls to play all the sounds but many of the sound files don't actually exist. For me when that happens the controls for the missing file didn't display so I knew that file didn't exist but for others the controls for non existent files do display. The only hint that the file doesn't exist is the length of time displayed would be 0.00 .
- Tim
